demo_dictionary_update.py

>>> dictionary = {"one":"one value", "two":"two value"}
>>> new_dictionary = {"foo":"foo value", "bar":"bar value"}
>>> dictionary.update(new_dictionary)
>>> print(dictionary)
{'one': 'one value', 'two': 'two value', 'foo': 'foo value', 'bar': 'bar value'}

>>> dictionary = {"one":"one value", "two":"two value"}
>>> new_dictionary = {"foo":"foo value", "bar":"bar value"}
>>> dictionary.update({**new_dictionary})
>>> print(dictionary)
{'one': 'one value', 'two': 'two value', 'foo': 'foo value', 'bar': 'bar value'}

>>> dictionary = {"one":"one value", "two":"two value"}
>>> new_dictionary = {"foo":"foo value", "bar":"bar value", "two":"updated two value"}
>>> dictionary.update(new_dictionary)
>>> print(dictionary)
{'one': 'one value', 'two': 'updated two value', 'foo': 'foo value', 'bar': 'bar value'}

A double asterisk ** denotes dictionary unpacking. Its operand must be a mapping. Each mapping item is added to the new dictionary. Later values replace values already set by earlier key/datum pairs and earlier dictionary unpackings.
https://docs.python.org/3/reference/expressions.html#dictionary-displays